Question

1. The unknown gas generating solid used is a well-known antacid, Alka Seltzer. a. What is the reaction occurring that produces gas? Include balanced chemical reaction. b. What is the identity and the molar mass of the gas produced in the Alka Seltzer reaction? c. Calculate a percent error for the molar mass using the formula:

2. The lab manual states “no gas leaks can be tolerated!” Discuss what the following errors or changes in procedure will have on your gas collection and on the calculated molar mass of your unknown gas: a. You did not replace the stopper quickly after adding the gas-generating solid. b. You stopped the gas collection and recorded the gas volume before the bubbling has stopped. c. The bubbling within the apparatus was vigorous and some HCl + tablet solution spilled into the hose through the test tube side arm. d. The apparatus accidentally picked up a few drops of water before the final mass was recorded. **Correct answers will clearly state if the calculated molar mass is higher or lower than the correct value or if there is no effect.

3. How does Alka Seltzer work as an antacid?

Answer 1

Q1.

a) Alka Seltzer is essneitally a base and an acid reacting to form CO2:

NaHCO3+C6H8O7+H2O=Na3C6H5O7+CO2(g)

the gas/bubbles are mostly CO2(g)

b)

Identity of gas is Carbon Dioxide, CO2

the molar mass of CO2 = 44 g/mol

c)

% error = (Real Molar Mass - Calculated Molar Mass) / (Real Molar Mass) * 100%

Q2.

No gas can leak, since we need this to relate to Total Pressure and volume of gas, this will let us know th eamount of moles, therefore we can relate moles of gas/alkasltzer used

a.

gas will leak, molar mass will be claculated lower

b.

the volume is lower, therefore, less moles, i.e. less molar mass

c.

there will be some reaction, so HCl reacts with the alka eltzer, expec tlower mass therefore, lower molar mass

d.

this will increase in correctly the molar mass due to increase in total mass

Q3.

Alka Seltzer works as antacid since it NEUTRALIZES acid

i.e. Alkja seltzer + H+ (protons of acids) will form a neutral salt, which lowers pH due to elimination of H+ in solution